Hemoglobinopathies, including sickle cell disease/anemia (SCD) and thalassemia (THAL), are the most prevalent inherited monogenic disorders in the human. Approximately 5% of the world's population carries a globin gene mutation. The World Health Organization estimates that each year about 300,000 infants are born with major hemoglobin disorders. SCD has segregated to populations from sub-Saharan Africa, India, Saudi Arabia, and Mediterranean countries, where up to 2% of all children are born with the condition, due to the survival advantage against malarial transmission conferred by a heterozygous sickle β-globin (βS) mutation (WHO Report on Sickle-cell anaemia—A59.9. Fifty-ninth World Health Assembly—Provisional agenda item 114: United Nations; 2006:1-5). Due to historic and/or recent migration, increasing numbers of patient populations can now be found in developed countries, and public health implications of SCD are significant (Kauf et al., American Journal of Hematology. 2009; 84:323-327; Amendah et al., American Journal of Preventive Medicine. 2010; 38:S550-556). In the United States of America, median survival of patients having a hemoglobinopathy was estimated in 1994 to be 42 years for men and 48 years for women (Platt et al., New England Journal of Medicine. 1994; 330:1639-1644). At a molecular level, SCD was the first disease to be linked to a molecular alteration (Pauling et al., Science. 1949; 110:543-548). A single nucleotide mutation results in glutamic acid to valine substitution by at position 6 of the β-globin protein. This modification results in the polymerization of the molecule in deoxygenated conditions, and subsequent “sickling” of the erythrocyte ultimately leading to anemia by hemolysis and acute and chronic vaso-occlusive and ischemic complications affecting multiple organs, including kidney, brain, lung, and others). Although preventive measures (including the chemoprophylactic agent hydroxyurea) have led to moderate reduction in the burden of selected patient groups, at present, the only available curative therapy for SCD is allogeneic hematopoietic stem cell transplantation (HSCT) (Hsieh et al., New England Journal of Medicine. 2009; 361:2309-2317; Hsieh et al., Blood; Electronic pre-publication Jun. 31, 2011). HSCT has unfortunately been associated in the SCD and THAL setting with significant mortality and morbidity, which is due in part to pre-HSCT transfusion-related iron overload, graft-versus-host disease, and high doses of chemotherapy/radiation required for pre-transplant conditioning of the host, among others.
New molecular therapies are being developed. For example, U.S. Pat. No. 8,383,604 describes that the BCL11A as a key regulator of the globin genes during development. In particular, BCL11A promotes the transitional switch from the expression of fetal hemoglobin genes to the expression of adult hemoglobin genes during fetal development. Suppression of BCL11A reduces this transitional switch and maintains a significantly higher expression of the fetal hemoglobin genes post fetal development. The higher amount of fetal hemoglobin genes expressed ameliorates the symptoms associated with various hemoglobinopathies.